U.S. patent number 4,389,793 [Application Number 06/238,407] was granted by the patent office on 1983-06-28 for wheel alignment apparatus.
Invention is credited to Louis L. Butler.
United States Patent |
4,389,793 |
Butler |
June 28, 1983 |
Wheel alignment apparatus
Abstract
An improved wheel alignment apparatus for the measurement in
four-wheeled automotive vehicles, of caster, camber, toe, steering
axis inclination, and track of the front and rear wheels. The
apparatus, which is employed with the wheels of the vehicle setting
on right and left alignment runways defining a reference plane and
direction of orientation for said vehicle, includes a tire contact
wheel clamp for each front wheel and a rear wheel. A tire contact
wheel clamp includes a set of orthogonally related gravity sensing
electrolytic transducers, and switching means are provided for
selectively recording or registering an output voltage proportional
to tilt angle of caster, camber, toe, steering axis inclination and
track of said wheels, as well as a phase indication of tilt
direction. Logic means receive the selective output voltages, and
an analog-to-digital converter provides a numerical displacement
output where there is tilt angle. A read-out, or numerical display
of the logic means is also provided.
Inventors: |
Butler; Louis L. (Baton Rouge,
LA) |
Family
ID: |
22897759 |
Appl.
No.: |
06/238,407 |
Filed: |
February 26, 1981 |
Current U.S.
Class: |
33/336;
33/203.14 |
Current CPC
Class: |
G01B
7/315 (20130101); G01B 5/255 (20130101) |
Current International
Class: |
G01B
5/255 (20060101); G01B 7/315 (20060101); G01B
5/24 (20060101); G01B 005/24 () |
Field of
Search: |
;33/335,336,337,288,286,203.12,203.18,203.14,203.13,365,266,228 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Haroian; Harry N.
Attorney, Agent or Firm: Proctor; Llewellyn A.
Claims
What is claimed and desired to be secured by Letters Patent is:
1. In an improved wheel alignment apparatus for the measurement in
four-wheeled, tired, automotive vehicles of caster, camber, toe,
steering axis inclination, and track of the front and rear wheels,
while the tired wheels of said vehicle are setting upon parallel
aligned runways, a right and left runway, defining a reference
plane and direction of orientation for said vehicle, the
combination which comprises
a tire contact wheel clamp inclusive of an elongate wheel bar at
each terminal end of which is located a laterally projecting wheel
bar clamp for operative contact of the inner face thereof with the
alternately disposed outer edges of a tire, one for horizontally
mounting on the outer side of each right and left front wheel, and
at least one other for horizontally mounting on the outer side of a
rear wheel,
orthogonally related gravity sensing electronic transducers mounted
on the elongate wheel bar of each tire contact wheel clamp, one
mounted at a right angle to the elongate wheel bar, and another
mounted parallel to the elongate wheel bar,
a flag assembly, one for each tire contact wheel clamp, inclusive
of a sliding member slidably mounted on a shaft parallel with a
runway connected via linkage to a flag bar mounted parallel to said
shaft for contact with a toe sensor plunger and toe calibration
adjustment screw located in circuit with the gravity sensing
electronic transducers,
electrical cables connected to and extending from each orthogonally
related gravity sensing electronic transducer providing multiplexed
electrical circuits,
a deck switch associated with each of said multiplexed electrical
circuits, providing electrical means for selectively switching from
one multiplexed electrical circuit to another,
logic means electrically coupled via electrical cables to said deck
switch,
an electrical generator which provides voltage signals over the
electrical cables to each of the gravity sensing electrical
transducers, the electrical transducers when associated with a
multiplexed electrical circuit via selective manipulation of the
deck switch to transmit to the logic circuit an output voltage
proportional to tilt angle of caster, camber, toe, steering axis
inclination, and track of said wheels, and
read out means for numerical interpretation and display of the
signals transmitted from said gravity sensing electronic
transducers to said logic means in terms of caster, camber, toe,
steering axis inclination and track of said wheels.
2. The apparatus of claim 1 wherein light-emitter devices comprise
said numerical display.
3. The apparatus of claim 1 wherein said tire contact wheel clamp
has means engaging contact with a rim edge of said wheel.
4. The apparatus of claim 1 wherein said transducer provide said
output proportional to the tilt angle between an input axis and a
horizontal.
5. The apparatus of claim 1 wherein said transducer provides an
a.c. output in response to a regulated square wave generator is
applied to the transducer, and said a.c. output is coupled to an
amplifier augmenting its nonlinearity and cut-off of diode
rectification characteristics near zero, an output of said
amplifier is coupled to a zeroing amplifier for adding a negative
component and for furnishing high impedance load characteristic to
the amplifier, which produces an output fed to said
analog-to-digital converter.
6. The apparatus of claim 5 wherein calibration means is connected
to said analog-to-digital converter to provide selected data input.
Description
CROSS REFERENCE TO RELATED PRIOR ART DISCLOSURES
The invention is an improvement and a departure over the
disclosures found and identified as follows: U.S. Pat. Nos.
2,177,669, Martin
2,603,881, Holaday
2,765,540, MacMillan
3,078,720, Hoffman, Jr.
3,675,495, MacMillan
3,865,492, Louis L. Butler
3,901,356, Louis L. Butler
3,901,604, Louis L. Butler
3,905,120, Louis L. Butler
3,906,810, Louis L. Butler
3,913,236, Louis L. Butler
4,150,897, Roberts, Jr.
None of these references and disclosures is found anticipative or
suggestive of the concepts of the present invention.
BRIEF SUMMARY OF THE INVENTION
The present invention relates to an improved wheel alignment
apparatus including a programmable compact sensing device to
determine and measure angles of caster, camber, toe, steering axis
incliniation (or king-pin inclination, K.P.I.) and track of the
vehicle wheels. More particularly the invention relates to a
programmed sensing device that easily attaches securely to the
wheels of the vehicle in a unique fashion with correct spatial
orientation to the wheel axis and using a commonly marketed and
used gravity sensing variable impedance electrolytic transducer
system that selectively measures angle of tilt provided in the form
of an output voltage proportional to tilt angle, and also provides
a phase measurement indicative of tilt direction when connected in
an appropriate bridge circuit and excited with an a.c. voltage.
The following terms are redefined here as follows:
CASTER--the slight usual backward tilt of the upper end of the
knuckle pin of an automotive vehicle employed as a means of giving
directional stability to the front wheels.
CAMBER--a setting of the front wheels of an automotive vehicle
closer together at the bottom than at the top; excessive camber
prevents the tire from having correct contact with the road.
TOE--a slantingly inward of opposed mounted wheels.
K.P.I.--king-pin inclination or steering axis inclination.
TRACKING--a setting of front and rear wheels in an alignment such
that the rear wheels are towed or follow in-track parallelism with
the respective front wheels.
BACKGROUND OF THE INVENTION
Apparatus for use in aligning wheels of automotive vehicles are
found to make measurements of four wheel alignment angles of
caster, camber, K.P.I. (steering axis inclination), toe and track
of the rear wheel.
Caster requires that measurements be made at a right angle to the
wheel assembly and that a vertical reference be established,
referencing the center assembly and that a vertical reference be
established, referencing the center line of the king-pin or
steering support arm to true vertical. The calculated values in
degrees or fractions thereof between the two vertical planes will
be the caster angle. The caster angle is commonly defined as the
forward or backward tilt of the king-pin or steering support arm at
the top.
Camber requires that measurement be made at a right angle to the
wheel assembly and requires that a vertical reference be
established, referencing the center line of the wheel assembly to
true vertical. The true value in degrees or fractions thereof
between the two vertical planes will be the true camber angle. The
camber angle is commonly referred to as the inward or outward tilt
of the wheel.
K.P.I. (king-pin or steering axis inclination) requires that
measurement be made parallel to the wheel assembly and requires
that a vertical reference be established referencing the center
line of the king-pin or steering support assembly to true vertical,
this value plus or minus the camber angle will be the calculated
angle of K.P.I.
Toe requires that measurement be made to determine the parallelism,
or deviation from parallel, of opposed wheels of a vehicle, either
the steerable wheels, the rear wheels or both.
Tracking requires that measurement be made to determine the
parallelism of all four wheels of a vehicle. The front and rear
wheels of one side of the vehicle referenced to the center line of
the vehicle and compared to the opposed wheels. All four wheels
should track in a straight ahead position.
There are many prior art devices for measuring the angles of
caster, camber and K.P.I., most devices utilize gravity seeking
sensors to determine or measure departure of this reference from
horizontal. Early devices used a pendulum or plum-bob with a
pointer attached thereto that is referenced to a scale or chart as
it departed from vertical. Martin U.S. Pat. No. 2,177,669 discloses
a spirit level device for measuring camber and caster angles;
MacMillan U.S. Pat. No. 2,765,540 shows an arrangement for
measuring such angles with a pendulum and a variable inductive
magnetic coupling arrangement; Holaday U.S. Pat. No. 2,603,881
discloses another approach which utilizes relative movement between
various reference components for varying electrical resistances to
determine these values; Butler U.S. Pat. No. 3,913,236 shows two
gravity sensing electrolytic transducers connected in an electrical
resistance bridge circuit that provides for remote readout when the
selected transducer is tilted to or away from a horizontal.
Prior devices such as described above have mainly been used to
measure angles of caster and camber only. Other arrangements which
were designed to provide types of readout, either locally or
remotely have been relatively limited, cumbersome, complex,
expensive and difficult to maintain and keep in calibration.
SUMMARY AND OBJECTS OF THE INVENTION
It is a feature, object and advantage of the invention to a wheel
alignment apparatus that provides
programmable information to electronically divide the sensing
capability of the sensors into known positions away from null in
each direction;
a multiple system-, time shared wires whereby multiple signals can
be carried by a single pair of wires;
an integrated circuit (I.C.) for each side, i.e., left and right,
and which is programmed to indicate all wheel alignment angles for
a designated side of the vehicle;
a L.E.D. display system that shows instantaneous indications of the
measurements and determinations as are sensed;
an on-board squaring circuit which eliminates value-change due to
line voltage fluctuations and which are controlled by voltage
regulators of a given voltage value;
a programmable arrangement that provides readout in degrees and
fractions of degrees;
a new clamping device attached to the tire of the vehicle wheel by
a unique arrangement referenced from the vehicle rim;
an index card system that is inserted in to the display panel and
shows, for a particular vehicle manufacture, preferred given values
of wheel alignment values and specifications for given vehicles in
digital values, said values being computed and translated from
inches and degrees or metric into known digital values campatible
with the logic of the present invention; and
modular construction of the component parts, a back-lighted center
cabinet which displays the illustrated angles of wheel alignment,
and which can be used as an instruction and training tool or
device.
It is another object of the invention to provide an improved
apparatus for measuring and determing camber, caster, toe, K.P.I.
and tracking of wheels on automotive vehicles and to adapt such
measuring and determining so derived for digital display upon a
L.E.D. of the values measured.
It is another object of this invention to provide a simple,
accurate and easy-to-use means of converting automobile
manufacturers wheel alignment specifications of inches and degrees
to digital values such as in degrees and decimal parts of degrees
and to readily display same for easy reference.
It is another object of the invention to provide apparatus of the
indicated type for measuring and detecting the desired values
through programmed electronic circuit means and which is simple to
align and calibrate and to maintain in accurate calibration.
It is another and further object of the invention to provide
apparatus of the invention to provide apparatus meeting the
aforesaid objects and which is of simple, economical construction
and which is easy to operate and reliable in use.
BRIEF DESCRIPTION OF THE DRAWINGS
The above and other objects and advantages of the invention will
become apparent upon full consideration of the following detailed
description and accompanying drawings in which:
FIG. 1 is a plan, partly in schematic form, showing a wheel
alignment apparatus according to a preferred embodiment of the
invention;
FIG. 2 shows in enlarged detail one of the wheel alignment
measuring details thereof;
FIGS. 3 and 4 show details in front elevation and side view,
respectively, of a wheel and its wheel clamp; and
FIG. 5 shows a perspective view of turning radius and roller plates
for each of the front wheels mounted on an alignment rack according
to use of the system of the present invention, and
FIGS. 6A and 6B show circuit schematic diagrams of the electrical
functions of the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE
INVENTION
Referring now to the drawings there is shown in FIG. 1 a wheel
alignment apparatus 10, left and right alignment runways 12, 14
supporting a vehicle 16 having a conventional vehicle wheels 20,
20, 20, 20 having front left and right sensing transducer units 22,
22 being retained in position on the respective wheels 20, 20 by
tire contact wheel clamps 24, 24.
A rear left (or right) wheel sensing transducer unit 26 is mounted
on rear wheel 20. Each transducer unit 22, 22, 26 are each
mechanically referenced to respective front and a rear parallel
flag assembly 28, 28, 30. While most alignment runway
configurations are installed parallel to one another, it should be
noted, however, the outboard parts of the wheel alignment apparatus
have means for parallel calibration. FIG. 2 shows in detail the
alignment runway 14 having wheel 20 on a turning radius and roller
plate 32 for availing the front wheel to turn about its axis and as
well to roll the wheel into track or runway alignment on which
there is pivotally secured the parallel flag assembly 28 which is
pivoted to linkage 34 which in turn is parallely linked to the
parallel flag bar or plate 36 which contacts a toe calibration
adjusting screw 38 mounted on the transducer unit 22 and also which
contacts a toe sensor plunger or feeler 40. By adjustment of the
roller plate 32 and the adjusting screw 38, the front and rear are
made parallel to the runway 14. Also shown in FIG. 2 is a
horizontal plane compensator 42 and a vertical plane compensator
44. The flag assembly 28 includes a round shaft 46 having a sliding
member 48 engaged thereon and adjusts to a position along the shaft
46 settles along the shaft as shown when the flag plate 36 is in
full parallel to the transducer unit 22 which in turn is in
parallel relation to the clamp 24. The clamp 24 has on its inner
end surfaces a set of line engaging projections 50 that extend into
the tire wheel 20 and a tightening adjustment nut 52 is used to
firmly secure the clamp on the wheel.
Cables 60, 62 extend respectively from sensing units 22, 22 to a
deck switch 64 in a control panel 66 in an instrumentation console
70. The 64 selects one of several multiplexed circuits from a left
or right sensor unit 22, 22 a signal indicative of castor, camber,
toe, K.P.I. or track which is coupled thence to left or right logic
circuit(s) 72 (FIG. 6A).
FIGS. 6A and 6B show a schematic of electrical and electronic
components within the console (70 FIG. 1) which includes a square
wave generator 76 that provides square wave signals over cable 60
to the sensor unit 22 having gravity sensing electrolytic
transducer 80 shown in FIG. 6 and from the square wave applied
thereto, there is an a.c. or square wave form output proportional
to angular displacement of the transducer from a normal vertical.
Such transducer known in the art is a 7660 Series, medium range
electrolytic transducer or the like that produces a smooth and
continuous output through a wide angle and when so connected such
as in a bridge circuit, the output is directly proportional to the
angle between the input axis and the horizontal. The instrument is,
manufactured by The Fredericks Company, Glass Components Division,
Huntingdon Valley, Pennsylvania 19006, (215) 947-2500. The unit
transducer provides the stability required for open-loop position
indicating systems in addition to being well suited for servold
applications. The gravity sensing electrolytic transducer 22 is
designed to provide an output voltage proportional to tilt angle,
and a phase indicative of tilt direction when connected in an
appropriate bridge circuit and excited with an a.c. or alternating
square wave voltage. It consists of a tubular glass envelope,
partially filled with an electrolytic fluid, with metal electrodes
in contact with the electrolyte, and such as have applications in a
system requiring a gravity reference or a tilt indication providing
a restoring or driving torque or tilt angle indication with the use
of proper circuitry and readout devices, namely guidance and
navigation systems, leveling and control of machine tools, platform
stabilization systems and measuring systems.
The output of gravity transducer 80 is fed to a precision rectifier
82 in logic circuit 72 uses its non-linearity and cut-off of diode
rectification characteristics near zero and its output is fed to
zeroing amplifier 84 which performs the three functions upon its
input of referencing to zero its received signal, adding a negative
component and it supplies a high impedance load to the output of
the precision rectifier. The output of the zeroing amplifier 84 is
coupled to an analog-to-digital converter 86 that processes the
signal to detect positive, negative and actual numerical
displacement from a reference zero and the output is multiplexed to
digital readouts 88. Connected to the A/D converter 86 there is
connected an adjustable calibrated reference voltage source 90 with
which to compare the output of the zeroing amplifier 84 for
establishing a selected slope as may be desired.
The transducer units 22, 22, 26 may each contains or includes two
gravity transducers 80 described above, each proportional
electronically to known values in each direction away from null
(true vertical) with one gravity transducer mounted at right angles
to the wheel and the other mounted parallel to the wheel. When the
sensing unit 22 is placed in a true vertical position, the set of
two transducers are mechanically adjusted to null in their
respective planes. Since the transducers are proportioned
electronically to known values, this is usually the only
calibration needed.
The gravity transducer that is mounted at right angles to the wheel
senses the values of caster and camber while the one mounted
parallel to the wheel senses the value of K.P.I. or steering axis
inclination. The logic circuit 72 provide for readily changing the
angular value of the caster-camber transducer as in determining the
caster angle and its signal output is processed for providing
remote L.E.D. readout of the measured values on readouts 88. Thus
the two gravity transducers comprise a set of orthogonally oriented
gravity sensing transducers; equivocally it can be shown that a two
axis gravity transducer may be constructed which permits
measurement of tilt angle in two axis simultaneously and when
connected with proper circuitry will provide a restoring or
measuring torque or indication for two axis operation.
The sensing unit also includes a potentiometer 96 mounted in the
sensing transducer unit 22. The potentiometer 96 is actuated by
means of a plunger or toe senser feeler 40 (FIG. 2) that moves the
pot wiper thereof from a known position. Like the two orthogonally
related gravity transducers described above, the potentiometer 96
is proportioned electronically to known values from a center
position of the wiper in each direction. Movement of the plunger in
either direction, in or out, will change the value which is
displayed on the L.E.D. display readout 88, and will indicate the
true value of toe. This requires that the flag plate 36, a straight
edge, is disposed in parallel relation to and in alignment with the
runways, as shown, and when the toe flag plates make contact with
the sensing transducer units 22 they will cause the potentiometer
96 and plunger or feeler 40 to be displaced which will indicate the
departure of the wheels from parallel thus indicative true value of
toe.
Cabling 60, 62 is connectable to unit 22 and control panel 66 by
cord and phone plug of conventional construction.
In the unit 22 includes a further track potentiometer 98 in the
rear wheel unit 26. The tracking device includes track
potentiometer 98 actuated by a "T" bar configuration that moves a
pot wiper when displaced from a known or given position, and like
the other sensor elements, the potentiometer is proportioned
electronically to a known value from the center position of the
wiper in each direction. The "T" bar is positioned parallel to the
alignment runways 12, 14 and the potentiometer is mechanically and
electrically calibrated to zero. When the "T" bar is placed
parallel to and against the rear wheel of a vehicle, the movement
of the pot wiper in either direction will change the value which
will indicate the track of the rear wheel as referenced to being
parallel to the alignment runway. A known position of the rear
wheel as in setting toe, described above, is significant or
important when centering the steering wheel 18 and setting the
front wheels in a straight ahead position. Similarly values of
track determined as described may be displayed by the L.E.D.
readouts 88, 88.
By switching the deck switch 64 in the control panel 66, for
example, in the `caster` position the angular caster values of the
front wheels 20, 20 may be displayed on the readouts 88, 88. Then
placing the deck switch 64 in the `camber` position the angular
camber values of the front wheels may be computed and selectively
displayed on readouts 88, 88. Further switching the deck switch to
`K.P.I.`, `toe` and `track`, the electrical values thereof are
displayed on the readouts.
In summary of track measurements described above, rear wheel
sensing unit 26 when mechanically compared and referenced to rear
flag assembly 30 will indicate digitally on left readout 88 a
numerical difference in parallel, if any, between the rear wheel 20
and the flag assembly 30. This measurement is important in
determining the track of the rear wheels and more especially to the
centerline of the steering wheel 18. Front wheel sensing units 22
when referenced to the front flag assembly 28 are seen to indicate
on the readout 88 the null or difference measurement between the
front wheels 20, 20.
There is shown in the perspective view of FIG. 5 a pit alignment
rack 110 for use with passenger cars and medium sized heavy duty
trucks and having wheel alignment apparatus 10 described in FIGS. 1
to 4 with left and right alignment runways 12, 14 for a vehicle
(not shown). The pit alignment rack 110 is mounted in a pit 114 and
the pit may have a depth of 30 inches up to 48 inches for allowing
more working room under the vehicle. Traveling air jack mechanism
118 provides means to lift the vehicle in a conventional
manner.
The turning radius and roller plates 32,32 comprise each a stacked
series of plates including, listing in series from the bottom to
the top, a base plate, a movable race plate with roller bearings
therein, a pivot plate, a pivotal race plate with ball bearing
disposed therein and turning radius and roller plate 32.
The turning plates may have a turning radius scale securably
mounted ahead of a wheel rest position proximate the pivot of the
plates mentioned above and the turning radius scale measures or
indicates angle left and right in degrees measured from 0.degree.
of straight ahead. Also the measurement of the angle left and right
may be indicated on the instrumentation console 70.
For purposes of providing two dimensional adjustments the sensing
transducer units 22, 22 (FIG. 4) may be provided with a
compensation spindle 122 on the wheel bar 126 disposed between the
wheel bar clamps 24, 24 and precise two dimensional adjustments are
provided by positioning and tightening wing nuts 130 on an
adjustable rim reference and vertical plane compensator 44, 132.
FIG. 6A shows a deck switch 64.
Additional embodiments of the invention in this specification will
occur to others and therefore it is intended that the scope of the
invention be limited only by the appended claims and not by the
embodiments described hereinabove. Accordingly, reference should be
made to the following claims in determining the full scope of the
claims.
* * * * *